1. Field of the Invention
The present invention relates to manufacturing devices, and in particular, to devices for polishing semiconductor wafers or substrates.
2. Description of Related Art
Chemical-mechanical polishing (CMP) is a well-known process in the semiconductor industry used to remove and planarize layers of material deposited on a semiconductor wafer or substrate to achieve a planar topography on the surface of the semiconductor wafer. To accomplish this, CMP typically involves wetting a rotatable polishing pad with a chemical slurry containing abrasive components and mechanically polishing the front surface of the wafer against the wetted pad. The pad is mounted on a rotary platen and a rotatable wafer carrier is used to apply a downward pressure against the backside of wafer. The polishing slurry is dispensed onto pad through a slurry dispensing arm during polishing. The force between the carrier and the pad and their relative rotation, in combination with the mechanical abrasion and chemical effects of the slurry, serve to polish the wafer surface.
Currently in a typical CMP, a high-pressure rinse (HPR) is applied by the slurry dispensing arm to the pad between wafer polishes, to remove pad debris, slurry residues, and foreign particles (loose conditioner tips, etc.). However, the slurry dispensing arm, which houses a high-pressure rinse delivery conduit, does not extend radially inward far enough toward the center of the pad on a 300 mm polisher. This leaves a significant amount of pad surface at its center with less coverage by the rinse system.
With reference to FIG. 1, a portion of a prior art chemical-mechanical polisher is shown. A pad 10 has slurry dispensing arm 12, which is orientated to be radially aligned with a center 14 of the pad 10. In a normal rinsing operation, the rotating pad 10 rotates under the stationary slurry dispensing arm 12 about center 14 at a constant angular speed. As shown by the curvilinear arrows 18 of increasing length, the velocity of a given reference point on the pad 10 increases as its distance from the center 14 increases. With reference to FIG. 2, the prior art slurry dispensing arm 12 is shown in detail. The arm 12 includes a high pressure delivery conduit 20 having a plurality of equally spaced rinse nozzles 22, with each nozzle having the same diameter.
There are at least two problems with the prior art design of FIGS. 1 and 2. First, the rotary platen (not shown) motion generates lower velocities at the inner radii of the pad 10, leading to slower particle motion towards the periphery of the pad 10, thus reducing the effectiveness of the rinsing flow. Second, a tip 16 of the slurry dispensing arm 12 is typically spaced-apart from the center 14 by approximately 4–6 inch distance, with FIG. 1 showing a 6 inch distance. Scratch data and associated model analysis show that the defects causing severe scratches are located inside or near the 6″ radius on the pad 10. This radius is approximately the location of the slurry arm tip 16, inside which the HRP coverage is not sufficient.